Page 264 - From Smart Grid to Internet of Energy

Cognitive radio based smart grid communications Chapter 6 235

as well as controlling spectrum sharing. Lastly, the cognitive HGWs should
effectively divide the possible spectrum bands between several smart devices
existing in the HAN and should administer the uninterrupted access of new
devices to the network by providing channels and IP addresses to each joined
device.

6.5.2 CR enabled neighborhood area networks

A NAN architecture can be considered as the second communication layer plat-
form for CR enabled SG systems as can be seen from the Fig. 6.17. This archi-
tecture may typically cover the areas in the range of several kilometers. The
main goal of the NANs is the enabling a communication bridge among customer
premises and electrical power systems in order to gather and control informa-
tion from the near terminals. The NANs can communicate with HGWs of the
HANs thanks to cognitive NAN gateway (NGW) structures that behave as cog-
nitive APs to assemble data from various HANs. Typically, a NGW may be
composed of a power substation, a utility pole-mounted device or a CR BS sys-
tem that can access to the HGWs over only one-hop connection [41, 42]. This
access opportunity can significantly enhance spectrum utilization efficiency in
a NAN architecture. A NAN system gathers power-related measurement data
from each customer connected to the network and delivers these data to the con-
trol center over the WANs in the SG systems.
Furthermore, in order to remove the leasing cost of licensed frequency
bands, the HGWs convey measurement data over licensed spectrum bands
by employing CR technology. Hybrid dynamic spectrum access method has
been also developed to efficiently transmit measurement data from the HGWs
to the NGWs [41, 79–81]. This access method employs licensed frequency
bands assigned by the NGWs in an opportunistic way for connecting to the
HGWs. Thus, the CR technology can improve the use of possible spectrum
bands to enhance the performance of the NAN networks. On the other hand,
the NANs are spread over very large areas including rural, urban and suburban
areas, and cooperate with the AMI systems that may employ different commu-
nication technologies based on the SG applications [41]. Since the NANs should
serve in large areas, various wired and wireless communication technologies are
adopted by these network schemes. In addition, the CR enabled NANs should
ensure a secure communication among the DAPs and the SMs [53].

6.5.3 CR enabled wide area networks
A WAN scheme that is the top layer of the SG communication architecture is
typically composed of various NANs as can be seen from Fig. 6.19. It enables
the broadband communication among distributed power generation systems,
substations, NANs, and control center of utility. This network utilizes a bidirec-
tional communication network with very high bandwidth that can accomplish